1. Field of the Invention
The present invention relates to an optical link apparatus to which an optical fiber cable is coupled for transmitting data.
2. Related Background Art
An optical link apparatus comprises either a light receiver unit or a light transmitter unit, or comprises both of them. The optical link apparatus includes lead pins and a link unit (sleeve) which protrudes from a package and which is coupled to an optical fiber cable. A light receiving device or a light emitting device is fixed in the optical link unit. As a ferrule which holds an optical fiber is inserted into a hole of the optical link unit, the optical coupling between the light receiving device or the light emitting device and the optical fiber can be achieved.
A metal package and a ceramic package have been used as packages for optical link apparatus; however, there are problems of productivity, processability and cost. As the countermeasure for these problems, an optical link apparatus to which a plastic molding technique, which is used in mass production LSI and which is superior in productivity and processability, is utilized has been developed.
As an optical link apparatus which is molded by a plastic, the structure of an optical link apparatus disclosed in "Japanese Patent Laid-Open No. HEI 4-329504 (329504/1992)" is shown in FIG. 1. A flexible substrate (lead frame) 40 is bent into L-shape and fixed on an island 6b which is for mounting a substrate. Electronic circuit components constituting a transmitter circuit and a receiver circuit are mounted on flat parts 40a and 40b of the flexible substrate 40, respectively. Further, a light emitting device and a light receiving device are mounted on vertical parts 40c and 40d, respectively. A transparent resin part 41 is formed on an external surface of each vertical plane 40c and 40d so as to oppose to a sleeve 4. Next, these devices and units are integrally sealed by a plastic molding. Thereafter, the unnecessary parts (e.g., a support part 6d, a separation part 6e, and others) are cut off, and the lead pins 6a are bent. Then, the optical link apparatus comprising an optical transmitter unit and an optical receiver unit is completed.
An optoelectronic integrated circuit (hereinafter called OEIC) in which an optical device and an electronic device are monolithically integrated on a semiconductor substrate has been researched and developed because compactness and high performance can be achieved. In particular, an OEIC in which a high electron mobility transistor (hereinafter called HEMT) which is a high speed electronic device or a heterojunction bipolar transistor (hereinafter called HBT) is fabricated on an indium phosphide (InP) substrate has been drawing the attention as a device for longwavelength optical fiber communications.
For example, an optoelectronic integrated circuit is disclosed in "An InP/InGaAs p-i-n/HBT Monolithic Transimpedance Photoreceiver, IEEE PHOTONICS TECHNOLOGY LETTERS, VOL. 2, No. 7, JULY 1990". In this OEIC, an HBT is used as a transistor.